Conventionally, a current sensor having a lateral type Hall element for detecting current flowing through a current path is well known. The lateral type Hall element is formed on a semiconductor substrate, and the Hall element detects a magnetic flux in a vertical direction of the substrate. The current sensor detects the magnetic flux by using the Hall element in a case where the magnetic flux is generated in a magnetic field when the current as a detecting object flowing though the current path. In the current sensor, the current path passes through a magnetic field concentration core having a C-shape, and a sensor chip including the Hall element is mounted between two ends of the C-shape of the core. Thus, the magnetic flux generated between two ends of the core in the vertical direction is detected by the Hall element. In this case, the concentration core is necessary for the current sensor. Accordingly, the dimensions of the current sensor become larger.
In JP-A-2003-262650, a current sensor including a magnetic sensor has a magnetic field concentration plate. The magnetic sensor includes a lateral type Hall element, and the magnetic field concentration plate is mounted on a top of the magnetic sensor. The concentration plate made from soft magnetic material concentrates a magnetic flux. The Hall element is mounted between two ends of the concentration plate so that the Hall element detects the magnetic flux in the vertical direction of a substrate surface. Thus, the current sensor detects a current. In this case, the current sensor has no magnetic field concentration core; and therefore, the dimensions of the current sensor become smaller.
However, although the dimensions of the current sensor are small, the magnetic field concentration plate is necessary for the current sensor. Thus, since a magnetic field concentration member such as the concentration core and the concentration plate is required for the current sensor, minimization of the dimensions of the current sensor is limited by the dimensions of the concentration member.
Further, in order to detect the magnetic flux caused by the detection object of the current accurately, the positioning among the current path, the Hall element and the concentration member is required to be more accurate. If the positioning among these three elements is deviated, the detection accuracy is varied. Thus, the detection accuracy of the current sensor is reduced.